1. Field of the Invention
The present invention relates to a sole for footwear, in particular for athletic shoes such as, for example, European football (i.e., soccer) shoes.
2. Background Art
Sports shoes are multi-functional. They fulfill a particular function in a respective discipline by supporting a particular movement or by providing good contact with the ground. They also function to protect the foot from exterior impact or to prevent wrong movements, in order to avoid injuries.
Risks of this kind arise in European football (i.e., soccer) when the player gets in contact with a ball. During this contact, enormous forces may act on the instep of the foot which hyperextend the foot in the direction of the sole (plantar), for example during a shot or when the opponent blocks the ball. In an extreme case, a player already having a high running speed may get his foot stuck in the ground. This leads to a sudden blocking of this high speed movement. The blocking may cause a plantar hyperextension of the foot and may lead to a painful injury.
The risk of such a plantar hyperextension could be effectively avoided by a rigid sole; on the other hand, this would disable the football shoe for fast movements since a rigid sole impedes an elastic rolling-up of the foot.
Several attempts have been made in order to provide a sole which is rigid against plantar hyperextension while simultaneously enabling rolling-up of the foot. Such attempts are also known for other areas of the shoe or for gloves.
The German utility model DE 19 73 891 describes a European football shoe which provides grooves in the area of the metatarsal whose side walls are provided with a layer which is harder than the material of the sole (see FIGS. 1 to 4). It is further suggested to also improve rigidity in the forefoot area by providing an extension away from the sole transverse to the longitudinal direction of the sole.
Similarly, the German patent DE 32 19 652 describes a European football shoe whose sole has areas with different degrees of hardness and which are arranged in the forefoot area. Recesses or grooves transverse to the sole are provided in order to save weight.
Further, the European patent application EP 1 074 194 discloses a structure for a sole in which alternating soft and hard elements are arranged as transverse grooves in a layer of a sole.
The published patent application US 2007/0107265 discloses a flexible sole with segments in the metatarsal area which can be articulated. However, this application is based on a problem opposite to that of the present application, namely to support a strong bending of the arch of the foot, for example during dancing.
Further, U.S. Pat. No. 6,715,218 describes a support device which is flexible in one direction and which is rigid in a different direction. This device can be incorporated into a variety of articles of sports equipment, such as sports shoes.
The German patent application DE 35 16 545 describes a goal keeper glove with elements on the backside of the hand, in order to avoid a hyperextension of the fingers to the back side.
The previous solutions against plantar hyperextension of the foot are not satisfactory since they impede the movability of the wearer of the shoe and do not fulfill general biomechanical requirements to allow smooth movements. Further, the manufacture of the described devices is complex.
It is therefore the problem of the present invention to overcome the disadvantages discussed above and to provide in particular a sole which avoids plantar hyperextension of the foot without limiting the movability during use of the shoe. Further, the sole shall be manufactured easily.